1. Field of the Invention
This invention relates to a large scale electrical interconnection system in which a plurality of electromechanical components can be electrically interconnected by an electrically conductive grid encapsulated within a insulative molding on which the electrical components can be mounted. More specifically, this invention relates to a harness subassembly in which a circuit panel subassembly comprising an electrically conductive grid, preferably in the form of a wire frame, in encapsulated within a reaction injection molded panel.
2. Description of the Prior Art
Electrical harnesses are typically made of electrical conductor wires which are mostly individually, stranded, and insulated wires with an occasional uninsulated stranded or solid wire utilized for grounding or the like. These wires are typically terminated by electrical terminals and/or connectors and formed into some general shape suitable for inventory and handling by the use of tape or harness ties. Fasteners may or may not be employed to affix the harness to the apparatus in which the harness is used. The harness wires serve the function of supplying power to the various components of such apparatus or signals for either control or machine intelligence purposes and, as mentioned, ground and/or shielding circuit functions. The harness may be a simple one, having only several short wires but a few inches in length utilized to interconnect the components of a simple circuit in an apparatus such as a camera or smoke alarm, or it may have literally hundred of wires terminated in very expensive connectors and utilized to interconnect all of the different devices and components of a complex circuit as in an aircraft. The harness constitutes a subassembly to be loaded into the apparatus on a production line as for example, with respect to appliances such as washers, dryers, copy machines, stoves, refrigerators and the like; or, added piece-meal as the apparatus moves along a production line. Generally speaking, a harness is a flexible assembly having a non-rigid shape, such as a plurality of discrete wires which are bundle tied together and terminated at ends thereof for interconnection to a panel or other end components. These harnesses are difficult to handle by machine, making it difficult to automate either harness making or harness handling or to employ robotic assembly techniques. Installation errors are common. This fact has frustrated industry for decades and, notwithstanding substantial efforts to automate or robotize harness making or harness manipulation, most harnesses are currently manufactured and installed in a highly labor intensive manner which impacts not only on cost but also on quality. One technique which has been employed is the use of a robot to deploy wires on a harness board. One example is shown in U.S. Pat. No. 4,593,452.
U.S. patent application Ser. No. 134,328 filed Dec. 17, 1987, discloses a method and apparatus for simplifying the wiring of an appliance such as a washer, dryer, copy machine, stove, refrigerator or the like. That application teaches a method of forming electrical wiring harnesses by implanting electrical wires into grooves in a panel laid out in a geometry or pattern suitable to effect wire distribution in the appliance. The panel can be formed from various materials including reaction injection molded plastics. The wires are terminated as desired by using an insulation displacement contact mounted in an insulated body which engages the wires as the wires are rolled in grooves past the insulation displacement contact. However, a single appliance may require a large number of different connectors. U.S. Pat. No. 4,684,765 discloses a bus assembly or harness formed by wires deployed on an insulative plate having a plurality of terminal stations.
Reaction injection molded panels have been used not only as a wire template as described above but have been widely used as structural components. Reaction injection molding differs from conventional molding in several aspects. In reaction injection molding two separate materials are injected into a mold. These component materials react with each other to form a cured part. These two component materials have viscosities which are much lower than a conventional thermo plastic or the reaction product of the two components. For this reason, a reaction injection molding can be conducted at much lower pressure than a conventional molding process, for example, at 100 psi as opposed to 4000 psi. Reaction injection molding also comprises a low temperature process which employs low viscosity materials. Reaction injection molding has been used to fabricate relatively large panels. Large panels fabricated using reaction injection molding processes can constitute three dimensional enclosures and metallic support brackets or screw fasteners can be molded in the reaction injection molded panels. U.S. patent application Ser. No. 324,162 filed Mar. 15, 1989, a continuation of U.S. patent application Ser. No. 272,167 filed Nov. 15, 1988, discloses an appliance cluster block formed using a reaction injection molded material.